Porsche Enthusiasts Club Forum

Hi, guys,
Just joined the forum last night and sounding out!!!
Ready to do a service on my 1991 944 Cabriolet.
Could you please advise best recommended oil?
Halfods have (had) special offer on 10/40W Part Synthetic on their website - any good?
Part number for sump plug washer - 900 123 049 30? or 900 123 118 30? - somewhat confusing from parts list!
Son's father-in-law has a 1987 944 2.5, sump plug washer part number?
Cheers,
Bob

10/40W semi will be fine. I errr.. always forget the new sump plug washer but pretty sure all 944s are the same. Halfords don't do the 944 filter but my big local factor does. They do Mann but KNECHT or similra will all be OK. Get a filter tool while in the factor as it makes getting the filter out a lot easier & also pop the lights up as it moves the linkeage out the way.

Hello and welcome, as Jim says above oil should be fine

10/40 semi should be spot, well thats what I just used anyway, and if the price has gone back up in halfords have a trip to Wilkinsons.... 7 litres bought as a 5 & a 2 (leaving you a little bit left over)...... Under £20

Now the thing is that mine is a daily drive so I burn a pint roughly once a month, and I'm of the opinion that a 20 odd year old car with over 170k under its belt isn't going to care much if I use wilko or Castrol Oil

As for the filter you could make life a lot easier next time by buying a K&N Oil filter with the nut on the top

But the tool is a fiver & I seem to remember the K & N filter is quite expensive!

Thank you gents for your advice,
The Halfords oil has indeed gone back up in price.
I shall look into the Wilkinsons tip, I am needing to do an oil change for two virtually identical cars - mine and my son's, so 3 x 5 litres would do the job!!
Plus an oil change on a 944 2.7L for the son's father-in-law - (he can get his own oil)!
All three cars being around 160,000 - 200,000 miles!!!!
Any specific advice on the sump plug washer - part number for the 944 S2's and the 944 2.7L?
Cheers,
Bob

Euro Car Parts - one part listed for all 944s, and 30 Pence only
Jeff

Thanks, Jeff, but therein lies my confusion!!!

Europarts listing is for Porsche part no. 900 123 118 30!

The Porsche parts manual, in addition to the above number, pictures and lists 900 123 049 30!
(I have a distinct feeling that 900 123 049 30 is the correct number for the sump plug washer).
The dimensions for these washers are different.
I didn't want to drain the oil and find the washer was the wrong size!!

I shall get under the car with my calipers and check.

Cheers,
Bob

Phone up an OPC and order a handful, Tonbridge, Exeter & others will post them out.

Thank, Jim,
Will do that tomorrow,
Cheers,
Bob

It would help you to know what the engine has been running on previously.
If it's a high miler that has been serviced with 20w50 for the last 25 years then the block is going to be full of sludge. The use of part synthetic oil in an engine such as this will cause, due to the detergent properties of the oil, said sludge to break away and block up oil galleries. It may also cause leaks around the sump and front timing case for the same reasons.

The enhanced ZDDP packages contained in modern oils certainly protects your engine a lot better than oils of old. However, the costs do not neccesarily outweigh the benefits.
On a fresh build, running in oil would be my choice and then a switch to a fully synth oil such as M1. However, for older engines with more than 100k on the clock which cruicially havent been serviced with a modern semi synth oil in the past 20w50 every 3k miles is the way to go.

In short - depends how the previous owners have looked after it.

-JC.

MGBV8.
Non Turbo engines don't need Mobil 1 (which isn't that great, but good marketing) or any other synth for that matter unless tracked or used on a circuit. Synthetics are purely for extended oil change intervals which are wrong on 944s anyway. You are also getting oil viscosities & types mixed. A 10/40W semi will be fine & won't promote leaks irrespective of mileage. In fact in my Alfa 75 it massively reduced oil consumption. Porsche recommend a wide band of viscosities in Northern Europe for oils either 10/40W or 20/50W. IF it has lots of sludge then why is that going to be broken away? The only oils I know of that removes sludge is very high detergent diesel type oils. Synth has no more detergent than mineral.
Personally I use 20/50W & change it often as mine uses oil. Most 944s are used as toys & barely do so more frequent oil changes with an average oil are better than some supposed super oil left for ever! If it is in average nick then use 10/40W as the tappets pump quicker.

TR7V8, I have a bit of an amateur interest in tribology, having ties to friends who run their own companies within the industry. This is a subject that interests me a great deal, so this post may well drag on a bit…

I certainly wouldn't use such a broad sweeping statement as "all NASP engines do not need a fully synthetic oil".
Firstly, the extended service intervals are purely down to the fact that the additive packages contained within synth oils work for longer before breaking down - a 20w50 grade that's been in an engine for 10k miles will be doing pretty much nothing to protect the white metal bearings and other load points where you have metal to metal contact, hence the short service intervals associated with this grade.
Secondly, it is a common misconception that just because a modern Vauxhall Vectra can run for 20,000 miles between servicing that the same should apply to a classic car. Bluntly, it doesn’t.
By modern standards, a 944 engine is a very dirty engine. So, whilst you still get the benefits of the better ZDDP package, decreased levels of friction and a greater shore rating which a fully synthetic oil provides, the contaminants will still build up in the sump more quickly due to dated engine technology being incapable of such a clean burn as our afore mentioned Vauxhall Vectra. Thus, despite the fact that the ZDDP package will still be working as efficiently as when the oil was first poured into the top of the engine, fully synthetic oil used in a classic type engine WILL require an oil change every 6000 to 7000 miles anyway since by this point the oil in the sump will have reached saturation point with carbon deposits.
So, this brings us neatly onto the next bone of contention; whilst the use of a fully synthetic oil has extended the service interval of our engine by 50%, A bottle of fully synthetic oil is still nearly 4 times the cost of a 20w50 grade. Whether it will have extended the life of the internal components sufficiently to justify the extra cost of the more expensive oil in the first place is a matter of debate and I suspect one that would not be resolved without bench testing two engines back to back. So, ultimately, the cost vs reward is left to the individual to decide upon for themselves.
Certainly if we were talking about an engine on the scale such as those that power a ship, then the cost of extra expense on maintenance is definitely worth it vs the cost of a rebuild. However, on an old car engine which is comparatively cheap to rebuild, then arguably, the use of a fully synthetic oil is unnecessary.



To argue that synthetic oils have “no more detergent properties than a base mineral oil” is incorrect. It all depends on the additive package that the manufacture adds to their base oil to create each blend. However, you are correct in that oils blended for diesel engines have higher detergent properties – different blends for different intended applications.

For these reasons, again, I would have to take a contrary stance to your opinion that fully synthetic oils do not promote leaks - the fact is, on an older engine, they will! Over time with the effect of continuous heat cycles the seals and gaskets used on all the mating surfaces of an engine will shrink. Gaps around these seals are then plugged with sludge and carbon deposits that inherently exist in dirty engines such as the engines we have in our cars. To introduce fully synthetic oil with its associated detergent properties to such an engine will cause this sludge to dissociate from where it was happily sitting. The absence of these sludge deposits now results in leaky seals around mating surfaces.

So, in a roundabout way, let’s go back to the original question that started this thread and expand upon it slightly;
There are two types of engines to consider:
New build and an engine in current service.

On a *New build* I would advocate running in on mineral oil and then switching to a fully synthetic oil. The decreased friction will free up a couple of horsepower for starters and the enhanced ZDDP package will protect your engine better whilst running and much better on start-up which is actually when most of the damage to a bearing surface is cause.

For an engine which is currently in service (and of more relevance to the author of the thread) it would help to know what it has been run on previously.
If it has been run on mineral oil all it’s life then the use of fully synth oil as previously mentioned will cause sludge deposits to block oil galleries starving the top end of oil and create leaks. Unless it is known for certain that an old engine has been run on fully synthetic oil for its whole life then it absolutely should not be use in an old engine – it will only create problems.
We are in agreement, therefore, that an older engine should only be run on 20w/50 mineral oil or a part synthetic 10w/40. However, I certainly wouldn’t worry about “mixing viscosities” between a part synth and a mineral oil since both oils are blended from the same base stocks anyway. It was fairly common practice before the introduction of so called multi grade oils to use oils with varying viscosities depending on the time of year.

As a closing point that may be of interest to members who, unlike you and I, are not “spanner men”; you rightly mention that a lot of these cars are used purely as toys. I would just like to pick up on that point for a second in that an engine certainly should NEVER be left with used oil in it over a long period of time irrespective of the grade!
If a car is to be left unused for a lengthy period of time, then an oil change should be done just prior to it going into hibernation – the deposits in used oil turn it slightly acidic. This acid oil over time will eat it’s way through white metal bearings – the very things you pour your oil in to protect! The fresh oil free from contaminants will then protect the engine internals without causing damage.
Cheers,

Jon.

Wow, very interesting and detailed comment, I wait for a response from Oilman

That is a "wow" from me, too, Jon.
I didn't wish to create friction - excuse the tribologist pun.....

To get back to basics - My car has done 180,000 miles; is in great condition mechanically; has had regular oil changes in it's service history (the last one being performed by the previous owner - oil make and type unknown, however).
The majority of these oil changes must have been with standard mineral oils (given the age of the car!).
I did an in-depth search as to which oil would be suitable for this car and the result was a unanimous pointer to 10/40W semi-synthetic!!!
I must admit I am of the old school and am used to a bog-standard 20/50W akin to Duckams and the like, but when this result surfaced, I was somewhat surprised and I plumped for a "basic" 10/40W semi-synthetic - namely Wilkinsons brand.
I, myself, am a qualified mechanical engineer and, in addition, a very much "hands-on" mechanic - I would not have entertained the "fully synthetic" oils mainly due to the cost, but surely, "semi-synthetic" oils MUST be better than pure mineral oils???
If built-up sludge is dislodged by this oil and finds it's way into the sump and ultimately the oil filter, is this not a good result?
But this result I somehow doubt - semi synthetic is not a "detergent" oil - like a diesel oil.
Clean oil-ways ultimately gives better lubrication!!!

In balance, I feel it better to use a good "semi-synthetic" as opposed to a regular mineral oil - bearing in mind that the oil change interval will not be extended!!
I (we) am looking at servicing 3 x Porsche 944's this weekend coming - mine, my son's and my son's father-in-law's and am confident that the oil chosen will do the job.

Oilman - what do you say?

Cheers, Bob